Electromagnetic flasher



United States Patent ELECTROMAGNETIC FLASHER Joseph Schmidinger, Lake George, N. Y.

Application August 19, 1952, Serial No. 305,103

13 Claims. (Cl. 307132) My present invention relates to electromagnetic flashers of the expansible wire type and comprises an improved construction of flasher of the above indicated type that, as compared to flashers now in wide commercial use, requires fewer and simpler parts, has greater magnetizing power and lower magnetic coil resistance, has greater stability against vibration and is less subject to functional failure. The new flasher is adapted for control of two circuits. It operates on the principle of the flashers disclosed and claimed in my U. S. Patents No. 1,979,349, dated November 6, 1934, and No. 2,103,278, dated December 28, 1937.

The patented two-circuit magnetic flashers of the expansible wire type comprise an electromagnet having two armatures each adapted to close a circuit in attracted position and one of which, the main armature, is spring biased to attracted position and the other of which, the auxiliary or pilot armature, is spring-biased to retracted position. An expansible wire is so connected under tension to the main armature that when the wire is cold or cool it holds the armature in retracted position and when it is heated, by passage of current therethrough, it expands and permits movement of the armature to attracted position. Movement of the main armature to attracted position shunts the wire and a ballast resistor in series therewith and thereby causes the circuit through the electromagnet to increase to a value suflicient to attract the auxiliary armature. Cooling and contraction of the wire, when shunted, causes retraction of the main armature, reduction of the current through the electromagnet and consequent release of the auxiliary armature under the spring bias thereof. The cycle then repeats with flashing of the circuits controlled by the armatures.

The novel features of construction of the new twocircuit magnetic flasher, which will be pointed out hereafter with more particularity, comprise an improved flat core construction for the electromagnet which provides broad pole faces, permits use of relatively short and broad armatures, and requires but a single layer winding while being highly efficient in utilizing available flux densities, a novel unitary armature, spring and Wire support assembly which can be readily mounted on the core and electrically insulated therefrom and novel and simple means for adjusting contact spacing for each armature.

For a better understanding of the invention and of the advantages thereof, reference may be had to the accompanying drawings of which:

Fig. 1 is a side view of a plug-in type two-circuit electromagnetic flasher embodying the invention;

Fig. 2 is an end view of the flasher of Fig. 1 taken looking in the direction of the arrows 2-2 of Fig. 1;

Fig. 3 is a plan view of the main armature assembly of the flasher;

Fig. 4 is a plan view of an insulating spacer used in the flasher;

Fig. 5 is a plan view of the core of the flasher;

Fig. 6 is an isometric view of a combined contact support and stop suitable for use with the auxiliary armature of the flasher; and

Fig. 7 is a circuit diagram showing use of the device in flashing a bank of lamps.

The elements of the new flasher are supported on a base 2 of insulating material to the under plane surface of which are secured terminal prongs 4, 6 and 8 by means of rivets 10, 12 and 14, respectively. The base 2 is formed at one corner with a shelf or platform 16 and with an upstanding shoulder 18 in the rear of the platform as viewed in Fig. l. A generally U-shaped core 20 of magnetic material having a relatively wide base 20a and wide and short legs 20b and 200 of unequal width, is mounted on the platform 16 by means of the rivet 14, the rivet clamping the base of the core adjacent leg 200 between the shoulder 16 and a plate 22 of magnetic material. The core 20 and sheet 22 are electrically insulated from each other by a sheet 24 of mica or the like disposed between the core and plate. Core 20, sheet 24 and plate 22 are provided with aligned holes for passage of the rivet 14 therethrough, the hole 26 in core 20 being large enough to provide clearance for the rivet and thus prevent electrical contact between the rivet and the core. Leg 20b of core 20 has a slot 28 near the side thereof to provide a bendable finger 30 upon which is mounted a contact 32. Weakening notches 32a at the base of the finger facilitates bending thereof. Leg 200 of the core has a lateral bendable projection 34 thereon connected to the leg by a restricted neck portion 34 thereon connected to the leg by a restricted neck portion 34a. A coil 36, comprising a single layer winding of insulated wire about the base 20:: of the core, has one end welded to the core and its other end con-- nected to terminal 4 by means of the rivet 10.

The main armature assembly of the device comprises the magnetic plate 22, a spring 38 having a curved section 38a and a hook-like extension 38b and an armature 40, the plate and armature being each welded to the spring to form a unitary structure for ready assembly of the flasher.

The main armature 40 at the free end thereof is turned upwardly and formed with a finger 42, to which one end of the expansible pull wire 44 of the device is anchored. The wire 44 extends under tension from the finger 42 to and through an insulating anchoring bead 46 of glass or the like mounted in an eyelet in an upwardly projecting finger 22a formed on the plate 22. Beyond the anchoring head 46 the wire 44 is loosely coiled and provides the ballast resistance 44a of the device. Mounted on the underside of the free end of the armature 40 is a contact 48 positioned for engagement with contact 32 when the armature is in attracted position. Spring 38 is welded at one end to the plate 22 and at its other end to the armature 40, the curved portion 38a being disposed between the parts of the spring which are welded to the plate and armature. The extension 3812 of the spring extends generally parallel to and along one side of the armature 40. At its free end the extension inclines upwardly and then extends transversely of the armature to provide a part 38c overlying the armature and operative to limit or suppress the extent of movemet of the armature away from the core. The insulating sheet 24, as shown best in Figure 4, is provided with a triangular opening 24a and with apertures 24b connected by slots 24c to the end of the sheet. When the armature assembly is mounted on the core a projection 22b on the rear edge of the plate 22 enters the notch 24a in the mica sheet and the shoulder 18 of the base causes the mica sheet to fold and bend upwardly, bringing the apertures 24b into position for support of the coils 44a of wire 44. The sheet 24 thus serves both as an insulating spacer and as a heat-proof ballast coil support. The end of wire 44 is welded to the core 2%) in the neighborhood of the contact 32.

The pilot or auxiliary armature of the device comprises an armature 48 which is mounted by means of a flat spring 5th on the underside of the projection 34 of the core. Spring 50 extends beyond the armature and at its free end is narrowed and bent downwardly to engage the base 2 which thus provides a limiting stop for the pilot armature. Mounted on the base 2 and supported thereon by the rivet 12, is a bracket 52 having an upstanding portion 54 provided with a rearwardly extending finger 56 overlying the armature 48 and spring "5% and serving, when the pilot armature is moved to at tracted position, to complete a circuit between terminal 6 and the core 20.

From the foregoing description it will be apparent that the electrical connections of the device illustrated in the drawing are as follows: From terminal 4- through rivet 10 and coil 36 to the core 20, from core through the ballast resistor 44a and tensioned part of wire 44 to the main armature and from the main armature through rivet 14 to terminal 8. Terminal 6 is connected to the core through bracket 52 and armature 48 when that armature is in attracted position.

The above-described electrical connections are il'ldl cated in the diagram of Figure 7 wherein terminal 4 is indicated as being connected to a source of positive po tential indicated by the symbol plus the negative terminal of which is assumed to be grounded, terminal 6 is shown as being connected through a pilot lamp to ground, and terminal 8 is shown as being connected to ground through a pair of parallel connected lamps 60.

In operation of the device, when current flows from a source of energy connected to terminal 4 through the winding 36, ballast resistor 44;: and wire 44 to armature 40 and thence through terminal 8 to a load such as the lamps 69, the wire heats and expands, reducing the tension therein and permitting spring 38 to move armature 40 to attracted position. When contacts 32 and 43 en gage, wire 44 and ballast coil 44a are shunted from the circuit. This increases the current through the lamps 60, causing them to light and increases the current through the Winding 36 sufliciently to attract the pilot armature 48 and thereby close the circuit of the pilot lamp 555 through finger 56 and terminal 6. When wire 44 is thus shunted, it cools and contracts until the tension thereof is sufficient to move the main armature to retracted position. The cycle then repeats. As the current through the device when the ballast resistance 44:: is in series with the load is insuflicient to light the lamps till, the pilot lamp and the lamps 60 will flash in unison.

The above-described device incorporates means for ready adjustment of the operating characteristics. The finger St) on the leg 20b of the core may be readily bent upwardly or downwardly from the plane of the core to adjust the spacing of the contact 32 from the contact carried by the main armature. The bias of the spring 50 which tends to maintain the pilot or auxiliary armature 48 in attracted position may be adjusted by bending the projection 34 upon which the spring 50 is mounted. The tension in the pull wire 44 may be adjusted by bending either the finger $2 on the armature or the projection 22-? of the plate 22. Similarly, the strength of the suppressor spring, the extension 38b of the spring 3%, may be vs ."l by bending the spring adjacent the end of the extension.

In the embodiment so far described, the base 2 in conjunction with the downwardly bent end of the spring limits the outward movement of the pilot armature 48. If an adjustable backstop for the pilot armature is desired, the construction illustrated in Figure 6 may be enrployed wherein a bracket 52a corresponding to bracket 52 and carrying a contact finger 56a for engagement with the pilot armature, is slit to provide a bendable finger 60 upon which may be mounted an insulating sleeve 62 for engagement with the armature 48 in retracted position. By bending finger 60 the outward movement of the pilot armature can be limited to the desired extent.

The above-described electromagnetic flasher is highly eflicient. The flat U-shaped core provides broad pole faces for mounting of relatively wide and short armatures thereon and thereby insures eflicient utilization of available flux densities. The wide base of the U and the close magnetic couplin of the main armature to the core insures high magnetizing power with relatively low magnetic coil resistance, a single layer winding providing ample magnetizing power for normal use of the device. As the only moving parts of this flasher are the armatures, and these are relatively short, greater stability against vibration is obtained than with flashers of low magnetizing power. The compact rnain armature assembly comprising the magnetic plate 22, biasing and suppressor springs and main armature, is simple to mount and well insulated electrically from the core while being magnetically coupled thereto. Assembly of the relatively few and simple parts of the flasher can be readily effected by mass production methods.

Although only a single complete embodiment of the invention has been illustrated and described, obviously various changes in the particular construction indicated could be made without departing from the spirit of the invention and the scope of the accompanying claims. Parts could be omitted while retaining the benefits attributable to the remaining structure. For example, al though the flasher has been described as a two-circuit flasher, obviously if a pilot or auxiliary circuit is not required, the auxiliary armature and terminal adapted to be connected thereto could be omitted without impairing the operation of the flasher under control of the main armature. Other changes or omissions, as for example, the provision of other than prong terminals or a different orientation of the elements on the base will occur to those skilled in the art.

I claim:

1. In an electromagnetic switch, the combination comprising a flat core of magnetic material having the shape of the letter U with a wide base and broad legs, the flat surfaces of the legs serving as pole faces of the electromagnet, a Winding on the base of the U, an armature of magnetic material, and means for insulatedly and pivotally mounting one end of said armature on one flat surface of one leg of said core, the other end of the armature being adapted to engage the corresponding flat surface of the other leg when the armature is in attracted position.

2. The combination according to claim 1 wherein the last mentioned leg is slit to provide a finger bendable toward and away from the armature.

3. The combination according to claim 1 wherein the leg carrying said armature has a bendable projection extending laterally therefrom, and wherein a second armature is provided, said second armature being springmounted on the surface of said projection opposite to that continuous with the surface of the leg upon which said first mentioned armature is mounted, the free end of said second armature extending toward the other leg of the core.

4. The combination according to claim 1 wherein said last mentioned means includes a plate of magnetic material overlying said pole face and electrically insulated therefrom, a leaf spring fixed adjacent one end to said plate and fixed adjacent its other end to said armature, and means clarnpin said core and plate together.

5. In an electromagnetic switch the combination comprising a flat core of magnetic material having the shape of the letter U with a wide base for accommodation of the winding of the electromagnet and broad legs, the flat surfaces of the legs serving as pole faces of the electromagnet, a first and a second armature, means for insulatedly and resiliently mounting one end of the first armature on one face of one leg for movement of the other end of that armature toward and away from the corresponding surface of the other leg and means for resiliently mounting one end of the second armature on the opposite surface of the first mentioned leg for movement of the other end of that armature toward and away from the corresponding surface of the other leg.

6. The combination according to claim 5 wherein said other leg has a slot therein providing a finger bendable toward and away from said first armature.

7. The combination according to claim 5 wherein said first mentioned leg is formed with a bendable lateral extension upon which said second armature is mounted.

8. In an electromagnetic switch, an insulating support formed with a flat supporting surface, a fiat core of magnetic material having the contour of the letter U with a wide base and broad legs, the base of the core adjacent one leg lying on said fiat supporting surface, a thin sheet of insulating material overlying the part of said core disposed on said surface and the adjacent leg of the core, a plate of magnetic material overlying said insulating sheet, means passing through alined holes in said core, sheet and plate support and serving to clamp said plate, sheet and core to said insulating support, a fiat armature springmounted on said plate over a leg of said core and adapted when in attracted position to engage the flat surface of the other leg of the core, a coil insulatedly wound on the base of the core, one end of said coil being electrically connected to said core, and at least two terminals mounted on said insulating support, one of said terminals being connected to the other end of said coil and another of said terminals being connected through said clamping means to said plate.

9. The combination according to claim 8 including a second armature spring-mounted on the leg over which said plate is mounted and on the opposite surface thereof and biased by its mounting to retracted position, a third terminal mounted on said support, and means engageable by said second armature when in attracted position for electrically connecting said third terminal with said second armature.

10. The combination according to claim 9 wherein said last mentioned means comprises a bracket fixed to said support and having a part overlying said second armature for contact therewith in attracted position, said bracket being split to provide a bendable finger underlying said second armature, and serving as an adjustable back stop for said armature, and an insulating sleeve on said bendable finger to electrically isolate said third terminal from said second armature when in retracted position.

11. The combination according to claim 8 wherein said plate has an eyeleted projection upstanding therefrom and wherein an expansible wire is insulatedly anchored in the eyelet of said projection and secured at one end under tension to the free end of said armature, the tension in said wire opposing said spring and acting when the wire is cool to hold the armature in retracted position, the other end of said wire being connected to said core, the part of the wire between the point of anchorage in the eyelet and the core serving as a ballast resistor.

12. In an electromagnetic switch, an insulating support formed with a flat supporting surface and with an upstanding shoulder adjacent one side of said surface, a flat core of magnetic material having the contour of the letter U with a wide base and broad legs, the base of the core adjacent one leg lying flush on said flat supporting surface and against said shoulder, a thin sheet of insulating material overlying the part of said core disposed on said surface and the adjacent leg of the core, the insulating sheet being bent through a right angle at the junction of the flat surface and shoulder and extending beyond the shoulder, a plate of magnetic material overlying the part of said insulating sheet disposed on said core, means passing through alined holes in said core, sheet and plate and serving to clamp said plate, sheet and core to said insulating support, a flat armature spring-mounted on said plate over a leg of said core and adapted when in attracted position to engage the flat surface of the other leg of the core, a coil insulatedly wound on the core, one end of said coil being electrically connected to said core, an cyeleted projection integral with said plate and upstanding therefrom, an expansible wire insulatedly anchored intermediate its ends in the eyelet of said projection and secured at one end under tension to the free end of said armature, the tension in said wire opposing said spring and acting when the Wire is cool to hold the armature in retracted position, the other end of said Wire being connected to said core, the part of the wire between the point of anchorage in the eyelet and the core being under no appreciable longitudinal tension and serving as a ballast resistor, the part of said insulating sheet extending beyond said shoulder serving to support said ballast resistor part of said wire, and at least two terminals mounted on said insulating support, one of said terminals being connected to the other end of said coil and another of said terminals being connected through said clamping means to said plate.

13. An electromagnetic flasher comprising in combination a fiat core of magnetic material and of the shape of a U with broad short legs and a wide base, a main armature insulatedly mounted'on the flat surface of one leg of the core, the other leg of the core carrying a contact positioned to be engaged by said armature when in attracted position, a winding on the base of the core, a fiat bendable projection extending laterally from said first mentioned leg, an auxiliary armature mounted on said projection and spring biased toward retracted position, said armatures being disposed on opposite sides of the core, spring means biasing said main armature toward attracted position, an expansible wire secured at one end to the free end of said main armature and insulatedly anchored under tension adjacent the mounted end of said main armature, the tension in said wire opposing the bias of said spring means, a ballast resistor connected in series with said wire between said main armature and said core so as to be shunted when the main armature is in attracted position, three terminal posts, one connected to said main armature, a second connected to one end of said winding, and means connecting the third terminal post to said auxiliary armature when in attracted position.

References Cited in the file of this patent UNITED STATES PATENTS 1,946,261 Zupa Feb. 6, 1934 2,103,276 Schmidinger Dec. 28, 1937 2,169,740 Peek Aug. 15, 1939 

